The flat-panel display devices such as LCD (Liquid-Crystal Display) devices or OLED (Organic Light Emitting Diode) display devices are widely used in various fields such as computer displays, TV sets, car navigation devices, personal digital assistants (PDAs) and mobile phones. Transparent protector sheets are attached on screen faces of display devices in mobile equipments such as mobile phones and PDAs, in on-vehicle devices such as car navigation devices and in some computer devices. The protector sheet curbs scratching on the screen face to avoid disturbance of visibility, and curbs damaging of the display panel even at a time the display device is fallen to ground or undergoes a strong impact.
In general, the protector sheets have been attached on casings of electronic devices and thus a gap is formed between the protector sheet and the display panel. Please see JP 1997 (H09)-008690A (Japan's patent publication application No. H09-8690). Meanwhile, it has been proposed to attach or paste the protector sheets directly on the screen faces of the LCD devices. Please see JP2004-325788A, JP2005-055641A and US2007/0046874A (JP2007-047621A) and JP1997 (H09)-133912A. This is to cope with problems of light reflection on glass surface due to existence of air layer in the gap and to decrease production cost of the display device.
The JP2004-325788A discloses followings in respect of attaching the protector sheet on the display panel on course of producing the display device. Firstly, ultra-violet (UV) curing resin is applied on a predetermined area on the display panel or on the protector sheet. Subsequently, the display panel and protector sheet are pasted with and then pressed to each other in a chamber vacuumed to absolute pressure of about 50 Kpa or less. Thereafter, vacuuming is relieved, and then ultraviolet (UV) irradiation is made at a non-displaying periphery area on the display panel as to achieve a “temporary bonding”. And, if a dust is found to be mingled in the adhesive layer by inspection using a CCD camera, the protector sheet is peeled off and then attaching of the sheet is made again. In the disclosed method, vacuuming is made at a time of pressing in order to curb inclusion of bubbles in the adhesive layer. Meanwhile, FIG. 4 of the JP2004-325788A shows following manners of applying the UV curing resin: dropping on only one circular dot at center; dropping on two to five circular dots having same diameter; dropping to form an X-shaped line pattern; and uniformly applying on whole of to-be-bonded area. The JP2004-325788A asserts in latter half of paragraph 0020 that; “As shown in FIG. 4, adoptable are one-dot dropping and multi-dots dropping, and no bubble inclusion is made by either of the methods.”; and by “the multi-dots dropping or uniform applying on whole of the area”, “decreasing of time for spreading the UV curing resin is achieved”.
Meanwhile, JP2004-325788A describes in 0019 paragraph as follow: “At absolute atmospheric pressure of 50 kPa, the LCD panel is brought onto the protector glass without causing air bubble if rate of approaching rate is set at 0.1 mm/sec”. This means that, even with some level of vacuuming, descending rate of the head has been required to be fairly small.
An LCD device disclosed in the JP2005-055641A has spacers that are formed of acrylic resin and are arranged on non-displaying peripheral area of the display panel at between the panel and the protector sheet; in order to achieve uniform thickness of a layer of adhesive that is filled and achieves adhesion between the display panel and the protector sheet. Meanwhile, the US2007/0046874A (JP2007-047621A) discloses an LCD device, in which “the protective plate includes fine concavity and convexity configurations on at least a surface thereof toward the display panel” (claim 1) so that “bubbles trapped . . . release from clearances between the concavities and convexities formed on the protective plate” (paragraph 0017).
Meanwhile, the JP1997 (H09)-133912A discloses a vehicle-mounted LCD device that has a resin sheet having a pressure-sensitive adhesion property and a shock-absorbing property, at between the LCD panel and a protector plate, in place of the adhesive layer.